This invention relates to the operation of a loom and relates more particularly to the method and means for monitoring and controlling the quality of fabric produced on a loom.
In order that fabric of acceptable quality may be made there are certain conditions in the weaving equipment that need be controlled. For example, defective feed of weft or warp yarns, broken yarns, or missing or improper filling yarns (picks) may result in defects in the fabric. It has been conventional in the art to have sensors and control mechanisms on the looms to stop the looms for manual correction of some defects. However, stopping the loom for fabric repair does not assure that the fabric ultimately woven will be of perfect quality. For example, since an improper pick is removed and replaced under operator control and since it is necessary to manipulate the fabric advancing mechanisms to insert a replacement pick, considerable opportunity for improper repair exists. Hence, it has been customary to inspect the fabric after it has been woven and removed from the loom and, if too many defects appear in the fabric, then it is graded to a lower quality.
It is an objective of the present invention to predict the fabric quality as it is woven and to operate the looms in a fashion such that fabric quality can be automatically and continuously predicted. Therefore, a problem resolved by this invention is the prediction of the quantity of potential fabric defects as the fabric is being woven with concomitant provision within the loom of means for processing predicted quality so that most fabric need not be further inspected.
Furthermore, the output efficiency of looms is significantly deteriorated by the requirement that the looms be stopped for correction and restarting under all conditions. Thus, in a mill with perhaps forty looms under surveillance of a single operator, several looms may be taken off line simultaneously while the fabric on only one can be repaired at a time. Accordingly, it is a further objective of this invention that defects be sensed and processed in such a way that the output quantity of the loom is increased and that stopping for repair can be avoided whenever looms are running at a low error rate.
To achieve these general objectives it is necessary to detect appropriate sources of potential fabric defects in the looms and set into motion corresponding control operations. Although it has been customary in the art to detect, for example, certain types of defects for the purpose of stopping the loom, these in general have been limited to detecting broken filling, broken warp, or missing filling. The system of U.S. Pat. No. 3,410,316 issued to J. Giuttari on Nov. 12, 1968 senses the presence of a weft yarn mechanically in a shuttleless loom by means of a movable feeler arm. Many other filling or yarn processing sensors are mechanical in nature and are not generally feasible for use in modern high speed shuttleless looms. Accordingly, electronic weft or filling sensors have been developed which operate to determine in the course of each pick period the presence of a pick.
Within the environment of air jet looms it has been convenient to sense the condition (presence or absence) of each filling yarn as it egresses from the air containment tube. Typically the following patents provide photo-electric sensors that may be located in the confusor element exit slot to determine the passing of a filling yarn out of the confusor: U.S. Pat. No. 4,085,777 issued to Z. Dadak et al. on Apr. 24, 1978; U.S. Pat. No. 4,150,699 issued to J. Suekane on Apr. 24, 1979; U.S. Pat. No. 4,188,901 issued to J. Suekane on Feb. 19, 1980; and British Pat. No. 1,236,346 of E. Sick published June 23, 1971.
Although these prior art sensors may be applicable for their intended purpose, there are certain types of critical yarn defect conditions in the weaving process that may not be discriminated without improvement in the sensing and control mechanisms.
Beyond the foregoing there are prior art systems for weaving machines to identify output quality and to decrease machine down time for mechanical repairs as, for example, set forth in the following documents:
U.S. Pat. No. 3,613,743 issued to T. Sakamota on Oct. 19, 1971 which applies an automatic fabric inspection apparatus to a loom to inspect and record the quality of fabric produced. This patent relates strictly a post-fabric formation inspection device.
U.S. Pat. No. 4,178,969 issued to M. Gotoh et al. on Dec. 18, 1979 which provides a system mode of operation which keeps weaving machines with lower machine repairs in operation awaiting off-line maintenance until higher priority repairs are corrected.
U.S. Pat. No. 4,146,061 issued to M. Gotoh on Mar. 27, 1979 where index yarn or yarns are inserted to mark fabric for identifying an event such as an improperly inserted pick as an aid in inspection and post-processing of the fabric.
None of the foregoing nor other known prior art predicts the quality of the fabric at the point of fabric formation. Neither does the prior art provide for operation of a loom in a greater output mode in response to a favorable high quality operating condition. These objectives are achieved by the present invention.